Field of the Invention
This invention relates to water-in-oil emulsions and more particularly stable water-in-oil emulsions containing polyoxyalkylene block copolymers.
Water-in-oil emulsions are useful in the preparation of cosmetics and pharmaceuticals, insecticides, etc. However, in the past it was generally believed that in order to create a stable water-in-oil emulsion it was necessary to employ, as an emulsifier, material that was soluble in the oil and insoluble in water. Water-in-oil emulsions employing such emulsifiers have the disadvantage that they are difficult to wash off the surface to which they have been applied. Accordingly, it is the purpose of the instant invention to provide water-in-oil emulsions for uses such as applications to the skin wherein the emulsion can be easily washed off. It is also a purpose of the invention to provide a stable water-in-oil emulsion of such type which is also non-irritating to the skin, non-toxic and colorless. The latter is desirable since if a color is desired it will be easy to obtain the desired color by use of a simple dye or other coloring material without being affected by the color of the water-in-oil emulsion itself.
U.S. Pat. No. 4,183,821 discloses crude oil demulsifier compounds which are block copolymers of tetrahydrofuran, propylene oxide and ethylene oxide.
U.S. Pat. No. 2,828,345 discloses surface active hydroxypolyoxyethylene diethers of polyoxybutylene glycols and that these compounds have emulsifying power in that they form stable oil-in-water emulsions.
An article by Kuwamura et al, Journal of the American Oil Chemists' Society, 48, pp. 29-34 (1971), entitled "Surface-active Block Copolymers: 1. The Preparation and Some Surface-active Properties of Block Copolymers of Tetrahydrofuran and Ethylene Oxide," discloses such surface-active copolymers.